Detecting the emergence of a projectile from the muzzle of a gun barrel



y 9, 1949- N. K. TURNBULL ET AL m DETECTING THE EMERGENCE OF A PROJECTILEFRO M THE MUZZLE OF A GUN BARREL Filed Jan. 12, 1938 M aasoumce I 3 Inventors Norman K -TurnhuL Attorney Patented July 9, 1940 Norman K. Tumbull, lfitman, N. J., andJames V. Dunham, Southampton, Pa.

Application January 12, 1938, Serial No. 184,636

(Granted under the act of March a, 1883, as amended April 30, 1928; 370 0. G. 757) UNITED STATES PATENT OFFICE The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to us of any royalty thereon.

This invention relates to detecting the emergence of a projectile from the muzzle of a gun barrel.

The main object of the invention is the utilization of the electric charge found to be present 10 in the gases escaping from the muzzle of a gun, and of the electric charge found on the barrel or other metallic parts of a gun upon the emergence of the powder gases therefrom, for operating various ballistic apparatus as hereinafter described.

With this and such other objects in view as may hereinafter more fully appear, the invention' resides in the use of the electric charge found in the powder gases and on the metallic parts of guns for changing the electrical potential of devices therein or connected thereto, and securing desired indicia therefrom.

' Practical embodiments of the constructon utilized are disclosed by way of illustration in the 25 accompanying drawing, wherein:

' Fig; 1 is a view of a collector mounted near the muzzle of a gun.

Fig. 2 is a schematic view illustrating the use of an oscillograph for indicating the presence of an electrical charge in the powder gases upon their emergence from the muzzle of a gun.

Fig. 3 is a schematic view of a circuit for detecting hangflres.

Fig. 4 isa diagrammatic view of a hangfire machine adapted for use with the present invention.

Referring to the drawing by numerals of reference:

40 There is provided a collector herein shown consisting of a ring I of conducting material of a suitable diameter secured to the bafile plate 2,

through which the gun muzzle 3 protrudes, by a rod 4 of insulating material and by tubular rod 45 5, in which is inserted a rod 6 of conducting material, rod 6 being secured to the collector lthe opposite end of said rod having connected thereto a lead wire I. The collector is placed the necessary distance in front of the muzzle and 5 centered thereon.

While there is shown and described a specific form of collector it is to be understood that the form used is immaterial as long as the collector is of conducting material, is insulated from 5 ground and gun and is in position to be contacted by the gases as soon as they emerge from the muzzle of the gun.

Although the electric charge found on the metallic parts of a gun upon the emergence of the projectile from the muzzle may be used to operate 5 any of the apparatus hereinafter described, it is necessary to insulate the gun from the ground. As this is usually inconvenient, the input of such apparatus as may be used is commonly connected to a collector rather than to the gun. 0

While in most instances the electric charge on the collector is sufilcient for the operation of devices that may be used therewith, the lead wire I may be connected to the grid terminal of an electronic amplifier 8, the other terminal of which is connected through lead wire 9 to ground.

A resistance l0 of from .50 to 10 megohms is connected across the wires 1 and 9. The output of the electronic amplifier contains the primary of an output transformer II, the secondary of which has one terminal connected through lead wire l2, and adjustable resistance I 3 to a terminal of an oscillograph II, the other terminal of the transformer being connected through lead wire IE to the other terminal of the oscillograph. A wire I6 connected to the lead I5 is grounded as shown.

' With the arrangement just described it is possible to indicate the instant of emergence of the projectile from the gun muzzle or in conjunction 80 with a firing pin and striker assembly which has been insulated from its bolt, to determine the elapsed time between the striking of the primer and the emergence of the projectile from the muzzle of the gun.

The electric charge may be utilized, in conjunction with any of the commonly used velocity screens, for operating any well known chronograph the construction and operation of'which are well known to those skilled, in this art and 40 are fully described in books on ordnance, for example, "Elements of Ordnance by T. J. Hayes. The circuit for indicating hangfires illustrated in Fig. 3 consists of the collector I, lead wire 1, I collector leakage resistor l1 and coupling condenser l8, one terminal of which is connected to the grid of gaseoustriode I 9. The biasing battery 20 has its negative terminal connected through grid resistor 2| to the grid of the gaseous triode, the positive terminal of said battery being connected through lead 22 to the cathode, the cathode being grounded through lead 23. Connected between the grid and cathode is grid protection condenser 24. The plate of the triode is connected through the primary of spark coil 25 to one terminal of charging resistor 21 by means of lead 26, the other terminal of said resistor being connected to the pwitive terminal of a full wave rectifier 28. A condenser 28 has one terminal connected to the negative side of the rec- 'tifier and the other terminal to lead wire 26. The negative side of the rectifier is grounded through lead 30. The secondary of spark coil 25 is connected to spark gap 3|.

From the foregoing it will be seen that condenser 29 is charged through resistor 21 from a source of direct current. Upon the emergence of the projectile from the muzzle of the gun, an electrical charge is picked up by the collector I from the ionized gases, this charge causing a change in the electrical potential of the grid of the gaseous triode l9, causing ionization of the triode. Condenser 29 being connected between the plate and cathode of the triode discharges through the triode and the primary of the spark coil 25. This discharge induces a high potential across the secondary of the spark coil to which is connected spark gap 3|, the spark across said gap being of sufiicient intensity to record on a tape, drum or disc or suitable material.

By rotating a small disc 32, with its periphery between the terminals of the spark gap, in synchronism with the same motor 33 as is used to control operation of the firing mechanism of an automatic gun 34, the sparks will record by perforating the disc in much the same manner as the bullets record by perforating the large discs used on the usual type of hangfire machines. The spark group may be measured in degrees from a preestabl ished zero point 35, any sparks falling outside of the permissible number of degrees being considered hangflres.

Because of the discharge of condenser 29 the plate potential of the triode is reduced to a point at which deionization takes place, the condenser again becoming charged after which the trlode isready to record the next round.

Through the use of this device, a small disc that may be easily filed for future reference may be arsed in place of the large discs commonly use By the use of a circuit similar to the one described Ior detecting hangfires, a light source maybe initiated having suflicient intensity to photograph a projectile upon its emergence from the muzzle of a gun.

We claim:

1. The method of detecting the passage of a projectile from the muzzle of a gun, which consists in collecting an electrical charge from the charge carried by the powder gases, then utilizing the effect of the same to produce desired indicia.

2. The method of securing data concerning the passage of a projectile from the muzzle of a gun, which consists in collecting an electrical charge from the charge carried by the powder gases, then utilizing the effect of the same to produce desired indicia.

3. The method of detecting the passage of a I projectile from the muzzle of a gun which consists in collecting an electrical charge from the charge present in the powder gases propelling the projectile and utilizing the collected charge to alter the electric current of associated mechanism.

4. The method of detecting the arrival of a powder gas at a given point which consists in collecting at said point an electrical charge from the charge present in powder gases, and then utilizing the efi'ect of the same to-produce desired indicia.

5. The method of detecting the arrival gas at a given point which consists in collecting at said point an electrical charge from the charge present in powder gases, and then utilizing the collected charge to alter the electric current of associated mechanism.

NORMAN K. TURNBULL. JAMES V. DUNHAM.

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